CHAPTER X. 



VARIATIONS IN NUMBER OF SPORANGIA. 



NOTWITHSTANDING the familiarity of the fact that the polysporangiate 

 state is the constant condition in Vascular Plants, little attempt has 

 hitherto been made to analyse the methods of variation in number of 

 the sporangia which they bear. But this would appear to be a promising 

 line* of enquiry, for it may be held that an adequate knowledge of the 

 methods of variation seen to be actually operative now should throw light 

 upon the factors which have been operative in the past, and thus some 

 suggestion should be obtained how the divers polysporangiate types came 

 to be as we now see them. To such an end the facts drawn from those 

 organisms which are held to be relatively primitive, such as the homo- 

 sporous Pteridophytes, will naturally bear greater weight than those derived 

 from more recent and specialised forms, such as the Flowering Plants. 

 Nevertheless it will be best to treat the question of change of number of 

 sporangia first of all in its relation to the Vascular Plants as a whole, 

 so that all the known factors may be disclosed : and it will be a matter 

 for subsequent discussion to decide in any individual case which of those 

 factors appear to have been operative in bringing that organism to its 

 present condition. 



The subject of variation in number of sporangia in the individual or 

 the race may be discussed either from the 'physiological or from the 

 morphological point of view : it is the morphological question which will 

 now be brought forward, though always in the light of physiological con- 

 siderations. But I wish at once to meet the objections of those who 

 will say from the physiological side that the number of sporangia depends 

 on nutrition : this self-evident proposition neither explains nor rules out 

 the morphological question how a plurality of sporangia arose, nor how 

 the great numerical differences which we see may have been attained : 

 nor does it modify the effect which observations of their numerical change 

 in the living individual, species, or genus may have on views of Descent 

 of the plants observed. By such observation and comparison of living 



